The present invention relates to an image display device. In particular, the invention relates to an image display device, which is also called a flat panel display of emissive type using thin-film type electron source array.
A type of image display device (field emission display; FED) has been developed, which uses emission type electron sources in micro-size and of integratable type, also called thin-film type electron sources. In this type of image display device, electron source is divided to emission type electron source and hot electron type electron source, etc. Those belonging to the former group include: Spindt type electron source, surface conduction type electron source, carbon nano-tube type electron source. Those belong to the latter group include: MIM (metal-insulator-metal) type with a metal layer, an insulator layer, and a metal layer laminated on each other, MIS (metal-insulator-semiconductor) type with a metal layer, an insulator layer, and a semiconductor layer laminated on each other, and thin-film type electron source such as metal-insulator-semiconductor-metal type.
The MIM type is described in the Patented Reference 1, for instance. As the metal-insulator-semiconductor type, MOS type is described in the Non-Patented Reference 1. As the metal-insulator-semiconductor-metal type, HEED type is disclosed in the Non-Patented Reference 2 and others. EL type is described in the Non-Patented Reference 3, and porous silicon type is disclosed in the Non-Patented Reference 4 and others.
The MIM type electron source is disclosed, for instance, in the Patented Reference 2. The structure and the operation of the MIM type electron source are as follows: An insulation layer is interposed between a top electrode and a bottom electrode. By applying voltage between the top electrode and the bottom electrode, electrons near Fermi level in the bottom electrode pass through potential barrier by the tunneling phenomena and are injected to a conduction band of the insulation layer, which serves as an electron accelerator. The electrons are turned to hot electrons and flow into the conduction band of the top electrode. Among these electrons, those reaching the surface of the top electrode and having energy of higher than the work function φ of the top electrode are emitted into vacuum space.    [Patented Reference 1] JP-A-7-65710    [Patented Reference 2] JP-A-10-153979    [Non-Patented Reference 1] J. Vac. Sci. Technol.; B11 (2); pp. 429-432, (1993).    [Non-Patented Reference 2] High-Efficiency-Electro-Emission Device, Jpn. J. Appl. Phys.; Vol. 36; pp. 939.    [Non-Patented Reference 3] Electroluminescence; Appl. Phys.; Vol. 63, No. 6, p. 592.    [Non-Patented Reference 4] Appl. Phys.; Vol. 66, No. 5, p. 437.
In the image display device using this type of thin-film type electron sources, electron sources are often destroyed due to unexpected electric charge or discharge during the manufacturing process or the display operation. In particular, the electron sources positioned on the outermost periphery of the display region are often destroyed. When electron sources are destroyed, display defect occurs, and all electron sources connected to data line may fall into display failure.
It is an object of the present invention to provide an image display device, free of display defects and having high reliability, by which it is possible to prevent the destruction of the electron sources as described above.
To attain the above object, the present invention provides a dummy potential fixing electrode, which does not contribute to image display and is similar to data line or scan line, on the outermost periphery of the display region. This potential fixing electrode is connected to an electrode with low impedance and constant potential.
The electric charge injected during the manufacturing process is absorbed by the dummy potential fixing electrode on the outermost periphery of the display region, and the electron sources for display operation are protected from destruction.